1. Field of the Invention
The present invention relates to a color filter for a liquid crystal display and a blank for forming a black matrix-screen to be used in fabricating the color filter.
2. Description of the Background Art
Generally, a color filter for a liquid crystal display, fabricated by forming an R layer (red layer), a G layer (green layer) and a B layer (blue layer) on a transparent substrate provided with a black matrix-screen is used to improve the visibility of the liquid crystal display. Generally, the black matrix-screen is fabricated by subjecting a blank provided with a screening layer of chromium or the like to plating and etching.
Recent demand for the further improvement of the display quality of liquid crystal displays requires, for the further improvement of the visibility (visual recognizability) of liquid crystal displays, a black matrix-screen for liquid crystal displays, having a front surface, i.e., a surface on the side of the transparent substrate (display surface), having a further reduced reflectivity in the wavelength range of visible radiations in addition to light screening capability.
FIG. 6 shows a chromium blank proposed in JP-A No. 61-39024 to meet such a requirement. As shown in FIG. 6, a chromium blank for forming a black matrix-screen, having screening capability and a front surface having a low reflectivity has a transparent substrate 610, and a two-layer chromium film 650 consisting of an antireflection film 620 of chromium oxide or the like formed over the upper surface of a transparent substrate 610, and a screening film 640 of chromium or the like formed over the antireflection film 620. FIG. 7 shows the dependence of the reflectivity of the chromium blank with incident light through the transparent substrate 610 on the wavelength of the incident light.
However, as is evident from a reflectivity characteristic curve L6 shown in FIG. 7, it has been impossible to produce chromium blanks of such a construction having reflectivities with incident light through the transparent substrate 610 of a desired value or below, such as 10% or below, for all the wavelengths in the visible wavelength range of 400 to 700 nm.
Furthermore, since the reflectivity characteristic curve L6 has a minimum at a specific wavelength in the wavelength range of 450 to 650 nm, the reflectivities for wavelengths are liable to change depending on the thickness of the antireflection film 620, causing changes in the saturation and lightness of the color of the reflected light.
Generally, the reflectivity characteristic curve has a minimum at a specific wavelength in the range of 450 to 650 nm due to the thin-film interference effect. Therefore, the specific wavelength changes according to the small variation (irregularity) of the thickness of the thin film. Consequently, the chromium blank has different reflectivities for different wavelengths, respectively, causing the variation of the color tone of the color of the reflected light.